discus vs mother-of-pearl

discus

noun
  • A discus fish (genus Symphysodon) 

  • The athletics sport of discus throwing. 

  • A round plate-like object that is thrown for sport. 

mother-of-pearl

noun
  • The hard pearly inner layer of certain mollusk shells; nacre. 

  • A butterfly of the genus Salamis. 

adj
  • Made from or looking like mother-of-pearl; iridescent or pearly. 

How often have the words discus and mother-of-pearl occurred in a corpus of books? (source: Google Ngram Viewer )